Association of Malassezia species with psoriatic lesions

The aetiology of psoriasis remains elusive. Among multiple factors hypothesised, association of Malassezia spp. is supported by response to topical antifungals. The objective of this study was to evaluate the association of Malassezia spp. with psoriatic lesion. The subjects included 50 consecutive patients with psoriasis, and 50 age- and sex-matched healthy controls. Samples were collected using scotch tape over one square inch area from the lesional and non-lesional sites. The isolated Malassezia spp. were identified by phenotypic methods and confirmed by ITS2 PCR-RFLP and sequencing of D1/D2 region of 26S rDNA. Psoriatic lesions were seen commonly on scalp (28%, 14), chest (22%, 11) and arms (16%, 8). Majority of cases presented with chronic plaque form (76%, 38; P < 0.05). From psoriatic lesions, most frequently isolated Malassezia species was M. furfur (70.6%, 24), followed by M. japonica (11.8%, 4) and M. globosa (8.8%, 3). From healthy individuals M. furfur, M. sympodialis, mixture of M. furfur and M. globosa was isolated in 73.3%, 10% and 16.7% (22, 3 and 5) of cases respectively. The average number of colonies isolated from scalp lesions of the patients was significantly higher (P = 0.03) than healthy areas. Although no strong association of Malassezia species was formed with psoriatic lesion in general, the fungi may play a role in exacerbation of scalp psoriasis.